Cruise Summaries

CRUISE SUMMARIES

Zigzag Transect Method

Used by NRCS foresters Simple and Quick way to determine

Average tree diameter Range of tree diameters Trees per acre Stand composition Stand Condition

Main Stand

Zigzag Transect Method

1. Select Main Stand 2. Choose a Route (X-section of stand) 3. Select a Starter Tree (unmeasured) 4. Choose a Direction 5. Locate Closest Tree of main stand 6. Determine Distance, Species, and

Diameter 7. Rate Tree Condition 8. Repeat until at least 20 sampled

Zigzag Transect Sequence

Zigzag Summaries + Calculations

Average Stand Diameter = sum of DBHs/# of trees

Range of Diameters – smallest tree to largest tree

Average Tree Spacing = total distance/# of trees

Trees per acre = 43560/spacing2

Percent of each species of all sampled trees

Stand condition = percent of each grade of total

Thinning Recommendations

D + x Rule of Thumb X usually equals 6, smaller for western

pines Example

If you determined that the average tree spacing was 12 feet, then trees per acre was estimated as

43560/122 = 303 If average tree diameter was 9 inches, 9 + 6

= 15 Ideal trees per acre = 43560/152 = 194 Thus 303 – 194 = 109 trees per acre need to

be removed to provide adequate spacing

COMPARINGFixed plot vs. Variable point

Cruises

Basal Area by tree size

Volume per acre by diameter

Summary of Major Points

Fixed Plot Variable Point

Sampling based on Frequency of occurrence

Tree size

Expansion Factor Same for all trees Varies by tree

Best for Total stems and number of small trees

Number of large trees

Best for Long term and repeated measuring

Temporary plots

Best for Distribution of DBHs Basal area and volume estimation

Tally determined Distance from plot center

Angle device over point

Misc Slope correction harder than angling

prism

Missing large distant trees, Missing hidden trees in dense stands

Expanding Measurements

Number of tallied stems for the tract by species

Average DBH, DBH range, QMD Merchantable Height (average number of

logs) Basal Area Estimates Board Foot Volume Estimates Cull Deductions Tree Grades

Trees per Acre

Number of trees measured can be expanded to express number of stems per acre for each species. There is no index of tree size. Generally more stems = smaller stems. Are they too crowded to grow well?

Trees per acre

A young natural stand of hardwood trees starts with 4000 to 6000 stems per acre. At maturity, when they measure about 20 inches in diameter, less than 100 trees per acre will survive. This is a natural selection process and it is slow, requiring 150 to 200 years or more to complete.

Mechanical thinning allows ‘crop’ trees room to grow at a faster rate, obtaining mature size in fewer years.

Crop tree release

Accelerated growthprovided byremovingcompetitors

Cost vs. benefit?

DBH

Could summarize and report average DBH of stems. If population isn’t normally distributed, this could lead to false conclusions. Adding an indicator of variance sheds more light.

Could use other measures of central tendency like median or mode.

Merchantability depends on that local mills are buying. (species, size, grade)

Average logs per tree

Merchantable height indicator of stand age and quality

When dominant trees harvested, most will have similar heights (total and merchantable)

Bucked into manageable sizes for hauling (16’ or less)

Each log graded for lumber yield estimate (more specific than standing tree grading)

Basal Area per Acre

DBH is used to calculate BA, cruise summaries should include this

BA can be used to calculate QMD

Area per area index.

60 ft2 of BA per acre by tree size

Volume per Acre

Takes your measurements to the 3rd dimension

Along with grade and species, used to assign value to stand

Stand Valuation = next topic